docs: def Kopte_Newell_Chato(x, rhol, rhog, mul, mug, m, D, g=g):
      r'''Calculates void fraction in two-phase flow according to the model of 
      [1]_ also given in [2]_.
      
      .. math::
          \alpha = 1.045 - \exp\{-1 - 0.342\ln(Ft) - 0.0268[\ln(Ft)]^2 
          + 0.00597[\ln(Ft)]^3\}
          
      .. math::
          Ft = \left[\frac{G_{tp}^2 x^3}{(1-x)\rho_g^2gD}\right]^{0.5}
          
      .. math::
          \alpha = \alpha_h \text{ for } F_t \le 0.044
          
      Parameters
      ----------
      x : float
          Quality at the specific tube interval []
      rhol : float
          Density of the liquid [kg/m^3]
      rhog : float
          Density of the gas [kg/m^3]
      mul : float
          Viscosity of liquid [Pa*s]
      mug : float
          Viscosity of gas [Pa*s]
      m : float
          Mass flow rate of both phases, [kg/s]
      D : float
          Diameter of the channel, [m]
      g : float, optional
          Acceleration due to gravity, [m/s^2]
  
      Returns
      -------
      alpha : float
          Void fraction (area of gas / total area of channel), [-]
  
      Notes
      -----
      [1]_ has been reviewed. If is recommended this expression not be used above
      Ft values of 454.
          
      Examples
      --------
      >>> Kopte_Newell_Chato(.4, 800, 2.5, 1E-3, 1E-5, m=1, D=0.3)
      0.6864466770087425
  
      References
      ----------
      .. [1] Kopke, H. R. "Experimental Investigation of Void Fraction During 
         Refrigerant Condensation in Horizontal Tubes." ACRC Technical Report 
         142. Air Conditioning and Refrigeration Center. College of Engineering. 
         University of Illinois at Urbana-Champaign., August 1998. 
      .. [2] Xu, Yu, and Xiande Fang. "Correlations of Void Fraction for Two-
         Phase Refrigerant Flow in Pipes." Applied Thermal Engineering 64, no. 
         1-2 (March 2014): 242–51. doi:10.1016/j.applthermaleng.2013.12.032. 
      '''
      G = m/(pi/4*D**2)
      Ft = (G**2*x**3/((1-x)*rhog**2*g*D))**0.5
      if Ft < 0.044:
          return homogeneous(x, rhol, rhog)
      else:
          return 1.045 - exp(-1 - 0.342*log(Ft) - 0.0268*log(Ft)**2 + 0.00597*log(Ft)**3)